We may begin by an important summary of Plato's philosophy given by Aristotle (_Met_. A. 6): "In immediate succession to the Pythagorean and Eleatic philosophies came the work of Plato. In many respects his views coincided with these; in some respects, however, he is independent of the Italians. For in early youth he became a student of Cratylus and of the school of Heraclitus, and accepted from them the view that the objects of sense are in eternal flux, and that of these, therefore, there can be no absolute knowledge. Then came Socrates, who busied himself only with questions of morals, and not at all with the world of physics. But in his ethical inquiries his search was ever for universals, and he was the first to set his mind to the discovery of definitions. Plato following him in this, came to the conclusion that these universals could not belong to the things of sense, which were ever changing, but to some other kind of existences. Thus he came to conceive of universals as forms or _ideas_ of real existences, by reference to which, and in consequence of analogies to which, the things of sense in every case received their names, and became thinkable objects." From this it followed to Plato that in so far as the senses took an illusive appearance of themselves giving {164} the knowledge which really was supplied by reason as the organ of ideas, in the same degree the body which is the instrument of sense can only be a source of illusion and a hindrance to knowledge. The wise man, therefore, will seek to free himself from the bonds of the body, and die while he lives by philosophic contemplation, free as far as possible from the disturbing influence of the senses. This process of _rational_ realisation Plato called Dialectic. The objects contemplated by the reason, brought into consciousness on the occurrence of sensible perception, but never caused by these, were not mere notions in the mind of the individual thinker, nor were they mere properties of individual things; this would be to make an end of science on the one hand, of reality on the other. Nor had they existence in any mere place, not even beyond the heavens. Their home was Mind, not this mind or that, but Mind Universal, which is God. In these 'thoughts of God' was the root or essence which gave reality to the things of sense; they were the Unity which realised itself in multiplicity. It is because things partake of the Idea that we give them a name. The thing as such is seen, not known; the idea as such is known, not seen. [252]